theflatlander

OK i've been having quite the dispute on how high both the 12a and and every generation of 13b can rev. This guy says he revs his internally stock GSL-SE to 9k and does so at least twice a day w/o any problems. I've been explaining to him the damage that he is and or will cause to his motor and he's just plain won't listen to me cause "he's owned so many rx-7s(9 total i believe and the motors ranged from 12a to 13b-rew)and has revs the **** out of all of them" mind you he has never done a rebuild, and has only really done bolt-on mods other wise it's been a shop or his friends doing the work. Now could i get some serious answers on what the limits of each motor is in stock form.

Lynn E. Hanover

That's a "How high is up?" question.



The RPM limit you want to hear about, is the one where the engine quits running for some mechanical reason. Barring a failure of some item that does not fail with regularity: The stock iron seals begine to bounce and cause advanced wear around 9,800 RPM. You have noticed some rotor housings with grooves along the hot side, that make them run like crap, power down, smoking, hard to start, no compression and so on. The stock seals are heavy and will not track over the sides of the peanut shape. One of those is between the spark plugs.



I would expect the first type of failure from an overrev to be a pinched corner seal. Just a bit down on power, until some other problem comes up. Not so much on a 12A but the longer shaft and heavier rotors of a 13B need a bit more clearance to keep the corners off of the irons.



The question he should answer is why is he reving so high. Unless substantial improvements in breathing have been made, reving past peak power very far is costing acceleration. You end up spending too much time on the back side of the power curve where HP is going down hill fast as revs go up.



Dyno the engine. Graph the HP curve. Calculate the area under the curve. (If you forgot all of that HS math you were so sure you would never need) draw the curve on graph paper and count the little squares.



Graph the trans ratios. Calculate the shift points that maintain the highest area under the curve for each gear change. Subtract a higher percentage of loss between gears as aero drag increases. Notice the need to maintain good power down low in the RPM range. Trade peak power for a better bottom end power

whenever possible. More area under the curve, higher avarage HP. Not higher peak HP.



Read all of the tech articals on Paul Yaws web site. www.yawpower.com







Lynn E. Hanover

jspecracer7

Great explaination Lynn. I'll keep that in mind before I rev to 9500 rpms.